<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .wrapper {
            background-color: #3a8ee6;
            height: 200px;
            display: flex;
            justify-content: space-evenly;
        }

        .flex1 {
            background-color: #5daf34;
            height: 200px;
            width: 200px;
        }

        .flex2 {
            background-color: #666666;
            width: 200px;
        }

        .flex3 {
            background-color: #e76f6f;
            width: 100%;
        }

    </style>
</head>
<body>
<div class="wrapper">
    <div class="flex1">盒子1</div>
    <div class="flex2">盒子1</div>
</div>

</body>
</html>